Agreed, why the hell not let them play? Afraid of making them competitive? Better ban sports and other games while you are at it, then....
For what it's worth, I learned Poker relatively young (early middle school), and we'd play with chips and everything. No money, of course, so I never really learned what the chips equated to in dollars (I could guess, as they were allotted points - some chip colors were 1 point, some 5, some 10, etc). Winning was the player with the most points. Plays like any other game.
And, as an adult now (and one who regularly makes business trips to Vegas), I don't gamble at all. Never have, in fact. I'm rather on the responsible side with my money and have no interest in participating in the "tax on people bad at math".
SO...I suppose that's the answer. Go ahead and let them play whatever "gambling" games there are (heck, even played roullette as a kid), but make sure they understand that, in the end, the house always wins and these are fun as GAMES and NOT investment strategies.
(In fact, it may be best to teach the *games* to them when they are young and only understand "fun" or "not fun" and money has no value to them. Then, as they grow up, they'll continue to see them just as "games" and not a way to make money - which is where the problem really lies. People who come to perceive gambling as a way to "strike it rich" are the addicts. People who play just to "have fun" don't have a problem - in fact, odds are, they won't end up playing at all. It's not "fun" anymore when real money is on the line)